Long distance telephone exchange system



March 1953 E. P. G. WRIGHT 2,633,501

LONG DISTANCE TELEPHONE EXCHANGE SYSTEM Filed Aug. 6, 1947 v 2 Sl-lEETS-SHEET 1 IN VEN TOR. ESMOND PHILIP GOODW/N WRIGHT ATi'ORNEY March 31, 1953 2 SHEETS-SHEET 2 Filed Aug. 6, 1947 INVENTOR. EJMO/VD PHIL/P aaaaw/u MIR/6H7 ATTORNEY Patented Mar. 31, 1953 LONG DISTANCE lTELEPHONE EXCHANGE SYSTEM Esmond Philip Goodwin Wright, London, Eng;

land, assignor to International Standard Eleotric Corporation, New York, N. Y a corpora;-

' tion' o'f Delaware Application August-6, 1947,. Serial; No, 7,66,136

In Grea -B ita i hrlt ifi Glaims.

This invention relates to long distance "telephone "exchange system.

*Theobject'ofthe invention'is "to facilitate the automatic setting up of international "connections between subscribers 'in different 'eol intries.

"The main feature of the invention comprises an international long distance telephone "exchange comprising international toll "lines incorning from exchanges in other countries, switching equipment accessible from said income mg tolllines fandgivin'giacc'ess to other exchanges within "the "same country, international toll lines accessible fromsaid incoming toll lines "and outgoing to exchanges in other "countries, international operator "positions, and "discriminating means associated 'with saidswitching equipment, but not'with said outgoing international toll lines, adapted to 'resp'ondto'a'signa'l arriving over an incoming toll'line to call in an international operator.

"The inventionwill be clearlyiunderstood from the following description of one embodiment shown in the accompanying drawings in which- Fig. 1 is aschematicrepresentation of certain switching elements involved 'in"'the setting up offia-n international connection.

"Fig. 2 shows the "re1evant ,portion s of the. circuits at an originating international. exchange concerned viith'setting up an international connectioniand calling in an international. operator at ithetermina'ting international exchange, while "Fig.8 showsportions of the circuits at a termin'ating international exchange for responding to asignal indicating that the assistance of an international operator ate-that exchange required.

Fig. 4 shows how the drawings are to be juxtaposed in order 'to illustrate the invention.

The main purpose of this inventionis to enable'an operator atan originating exchange, for exampleExehangeT1 (Fig.1), to call. in-a particular one of a number of operators located along the vroute of a 'built-up. connection establishedthrough anexchange, for example Exchange'3', .which islocatedina different country from that of exchange '1, 'viaan intervening exchange, for example Exohange z, which.may hejlocated'invyet anotherv country. One example of the use of the invention would occur. in international telephony where an operator in'the originating country desires to call an international operator intheterminatingcountry without calling'in anoperator inan intermediate country through which the connection .may' have been e up- I is .pqss blethat i-the o erator 11. Ellie try ton line ITLI are i or n ti countr i'xnav h nhan e a tho e hasdia le Ifa ISm t8d 'th-3PP reachth'e calledsuhscriber; ch conditions can arise when theisai'd 'operator periences l I yljhe fealled u s er "It is cell an QP- r w in "t erm ene 0 nitry he ause the originating operator n ay'n bejfableto speak he na n l an a e fit 1 .1. ,s co try. howeye'r ianiinterna o operator is a n,.1an ua e i W111 e: err rne'. n't m o en il-lu lre ditheinre tiqnhes been 'appli'ed'to a system in, which dial n pulses and other control signals *a'retransmitted over toll lines by v meansof,alter ting currents at one or the other of we" c d frequencies inll' d' i in ih 311 59165? Qft 'W C in such".twO Y iiG, ire uency": j na11 nesystems. the selected frequencies are ,qgmmonly 1'. known as the X frequency and the Yi "ifrequency. In Fig. 1,.the operator .positi njQPl and the outgoingtrunk ,OTQI andiyo v equencyfsignal transmitter-VET! yasso ted 'ith an inter-coun- Ja re n tmei ter a tional exchange i ,1 in ryi 0P2 :is n n na o a iopera qnino i m am a e national exchange 52 in ga'jsecond. country; :82! is an'incoming selector, .conventionallyrepresented, terminating the toll .Tline "I' l'.ZLI,.; I VFR2 is .a ,voice-frequenc'y signal rece iyer and relay .set associated withthe incomingendof the toll line ITL l; selector S2! has. access' over -,certain of its outletseto inter-country lltollllines', suchas toll line ITL2, having an .outgoingrelay -set ICZZ and leading to an international; exchange 3 in .a third country, and over others of its outlets to trunks leading ,to 1O0 :t1.- .S e1QQI?S,.-;Slll3 h, as selector S2 2,,v said .trunks -having anappearance on .the international operator posit on B2,.via operator answeringtrunlgs such as runlr QATZ selector S22 has aocess over certainof its outlets to intra-country toll ..lines, ,suohi a's ,toll ,line" T1 2, ng to the x ha'e e Lin j h e country; the international. operator at position 0192 may alsohe given a ccess:: to the toll line ITLZ, .via trunks .such..as,.j-trunl r 0T2. 0P3, .33 l ITL'LZ, .'VF?R 3, IT f 3 11 013,332,- OAYI- 3, Th3, and 0T3 are corresponding eleinents position and circuit respectively in an international exchange ts ue'to' he was 3Qin a third country; selector-$32 hasaccess. over ance on an operator position P4, via operator answering trunks such as trunk OAT4; VFR4 is a voice-frequency signal receiver associated with the trunk leading to selector S32.

It is to be understood that the position 0P3 is stafied by an international operator capable of giving assistance on a connection originating in another country, whereas the operator at position 0P4 may not be so qualified; also that at exchange 2, there may be signal receivers, selectors, operator positions and trunks corresponding respectively to the elements VFRA, S33, 0P4, OAT i and TL at exchangejl. g

The operator at position OPI, upon setting up a connection via toll line I'ILi, selector SZi, toll line ITLZ, selectors S31, S32 and S33 and other selectors, not shown, to a subscriber in the third. country, may experience language difficulty in conversing with him and may therefore desire to obtain the assistance of the international operator at position 0P3. It is required that the signal which the operator at position DPl uses to call in the operator at position 0P3 shall not be eiiective at position 0P2 or 0P4.

Had the connection been set up via selectors S21 and S22 to a subscriber in the second country, then the operator 'at position OP! would have wished to call in the operator at position 0P2. Similarly, had the connection been set up via selectors 32%, S3! and an inter-country toll line ITL3 to a subscriber in yet another country, the operator at position OPS would have wished to call in an international operator in that country, rather than the operator at position 0P3.

Figs. 2 and 3, when juxtaposed as indicated in Fig. 4, show means for calling in an international operator at position 0393 for a connection set up by an operator at position OP! via selectors S21, 83!, S32 and S33.

Fig. 2 shows the essential portions of the circuits at exchange 1. ID are the impulse springs of a calling dial and lFT is a forward call key, both forming part of the operators equipment on position OPI lki, iIcZ, l7c3 indicate any conventional means for associating said operators equipment with a voice-frequency signal transmitter VFTI when connection is made with the outgoing trunk OTi via the calling jack CJ; the signal transmitter includes transformer 4T and relays IA, lB, l3? and HI.

Relay iA operates when contact is! closes and the contact l'ai closes an obvious circuit for relay IB, which in turn closes a circuit for relay IY at ibi. Relays 1B and iY prepare the forward signalling circuit over toll line I'ILl at i123 and I112.

When the dial is operated, relay A restores intermittently and connects the A. C. generator GEN. X via contacts [a2 and 122 to the middle winding of transformer lT, causing corresponding trains of current impulses at frequency X to be transmittm over toll line ITLI. Relay IB is slow-to-release and remains operated during the trains of impulses. In accordance with well-known switching practices, these dialcontrolled trains of impulses control successively the incoming selector S2: at the exchange 2, l, to extend the connection to a toll line ITL-2 leading to exchange 3, and thereafter the incoming-selector S31 (as will be described in greater detail hereafter), the selectors S32 and S33 and other selectors, not shown, to select the wanted subscriber. V If the originating operator encounters language dimculty with the called subscriber, she can call in an international operator at the terminating international exchange by momen tarily actuating the key IFT. When the key IFT is operated, relay IB is released and relay IF operates; the A. C. generator GEN. Y is connected via contacts lyi, H2, R22 to transformer IT until the slow-to-release relay IY is released by contact lfl and opens its contact lyi, thus causing a single burst of current at frequency Y to be transmitted over toll line I'ILl to call in the desired operator.

Fig. 3 shows parts of the incoming selector 63!, the local selector S32 and the operator position 0P3 at the terminating international exchange 3. Voice-frequency signals transmitted as described from exchange 1 reach selector S3i via exchange 2 and toll line ITL2 and pass via transformer 2T into a voice-frequency signal receiver VFR3, which may be of any well known type which includes devices responsive to the signal frequencies X and Y. When a signal at frequency X is received, relay 2X operates, while a signal at frequency Y operates relay 23?.

The first train of impulses at frequency X thus causes contact 20:! to close a number of times and to operate the magnet SISM of selector S31, raising the wipers WI, W2, W3, W4 to the bank level to which selector S32 is connected; relay 20 operates in parallel with magnet BISM and, being slow-to-release, remains operated until the end of the train. When the impulses cease, relay 2C restores and the conventional hunting operation for a free outlet in the selected level follows; relay 2H operates in series with the resistor RI in selector S32 when the outlet leading to' this selector is reached; relay 2H extends the connection thereto at contacts 2h! and EM.

The next train of impulses at frequency X causes selector S32, by means not shown, to extend the connection to selector S33 and the remaining trains cause the connection to be completed via toll line TL4 and other selectors to the wanted subscriber.

If now a pulse of current at frequency Y arrives over toll line ITL2, Fig. 3, relay 2Y operates and at contact Zyi closes a circuit over wiper W4 for relay 2K in selector S32; relay 2K locks to ground at contact 2cl via resistor R2, contact 2k], wiper W3 and relay 2H, thus remaining operated after the cessation of the pulse. At con-' tact 2E2, relay 2K closes a circuit for calling lamp CL to attract the attention of the operator at th international position 0P3. The said operator can now enter the connection to give the desired assistance by plugging into the jack AJ connected to the operator answering trunk OATZ.

Had the connection been routed from selector S31, Fig. 3, to a toll trunk ITL3 leading to another country instead of to selector S32, exchange 3 would no longer have been the terminate ing international exchange in the connection and the operator at position 0P3 would not have been called in by the Y frequency pulse passing through the relay set 103, because said relay set is not provided with discriminating means, such as relay 2K in selector S32, connected to the bank contact on which wiper W4 would have been standing.

By the same token, with reference now to Fig. l and to the connection previously described, the Y frequency pulse, which operates a relay in selector S2! at exchange 2 as well as relay 2Y in selector S31 and which also passes through the relay set 1C2, does not cause the operator at position 0P2 to be called in, because said relay set is not provided with discriminating means for this purpose. Furthermore, the circuit with which position 0P4 is associated does not possess such discriminating means and only an international operator and not a national operator at the terminating international exchange 3 is called in by the Y frequency pulse.

It will be understood that there may be a number of intermediate switching centers similar to exchange 2 between the originating and the terminating international exchanges, all of which will behave in the manner described for exchange 2.

I claim:

1. A system for establishing telephone connections between subscriber stations in diiTerent geographical areas, comprising an exchange in a first geographical area, an'incoming selector in said exchange provided with a signal receiver, an inter-area toll line extending to said incoming selector, local selectors accessible to said incoming selector and having access to subscriber stations in said area, other inter-area toll lines accessible to said incoming selector and having access to subscriber stations in other areas, an operator position at said exchange having access to said local selectors and to said other toll lines, a calling device at said operator position, means controlled by said signal receiver responsive to signals of one character received over said toll line and adapted to extend a connection via said incoming selector to one of said subscriber stations, signalling means in said signal receiver responsive to a signal of another character received over said toll line, and discriminating means controlled by said incoming selector and efiective only when'said connection has been extended to one of said local selectors to cause said signalling means to operate said device.

2. A system was claimed in claim 1, wherein said signal receiver includes means for accepting alternating current signals, said signals of one character comprising trains of pulses at a frequency included in the frequency range of the voice, and said signal of another character comprising a pulse at another frequency included in said range.

3. A system for establishing telephone connections between subscriber stations in different geographical areas, comprising an exchange in a first geographical area having a first operator position, a second exchange in a second geographical area having an incoming selector, an interarea toll line extending from said operator position to said incoming selector, local selectors accessible to said incoming selector and having access to subscriber stations in said second area, other inter-area toll lines accessible to said incoming selector and having access to subscriber stations in other areas, an operator position at said second exchange having access to said local selectors and to said other toll lines, a signalling device at said operator position at said second exchange, means at said first operator position for transmitting signals over said toll line to extend a connection via said incoming selector to one of said subscriber stations, means at said first operator position for thereafter transmitting a characteristic signal over said toll line, signalling means associated with said device, and discriminating means controlled by said incoming selector and effective only when said connection has been extended to one of said local selectors to render said signalling means responsive to said signal for operating said device.

4. A system as claimed in claim 3, wherein said signalling means comprises a relay associated with one of said local selectors and actuated in response to said characteristic signal.

5. A system as claimed in claim 4, further comprising means for maintaining said relay actuated after the cessation of said characteristic signal.

ESMOND PHILIP GOODWIN WRIGHT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

